update rp2040 warnings

- remove "-Wno-stringop-overflow -Wno-array-bounds"
- skip -Wconversion for gcc 9 and prior
- suppress_tinyusb_warnings only when building with gcc 9 and below

examples/device/hid_composite/src/main.c

@@ -230,7 +230,7 @@ void tud_hid_report_complete_cb(uint8_t instance, uint8_t const* report, uint16_
   (void) instance;
   (void) len;
 
-  uint8_t next_report_id = (uint8_t)(report[0] + 1);
+  uint8_t next_report_id = report[0] + 1u;
 
   if (next_report_id < REPORT_ID_COUNT)
   {